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Fuel Pressure Regulator Diagnosis: Notes

WARNING: This page is about a different car, the 2019 GMC Savana 3500, 2019 GMC Savana 2500, 2019 Chevrolet Express 3500, and 2019 Chevrolet Express 2500. However, it is still accessible from the selected car via links, so may be relevant.

The Fuel Pressure Regulator graphing procedure offers valuable information on regulator performance by comparing desired and actual fuel rail pressure. An almost perfect comparison between fuel rail pressure and desired fuel rail pressure is found on low mileage engines. A minor ripple is acceptable behavior for the fuel rail pressure regulator and is seen on high mileage engines. A "shark tooth" fluctuation in fuel rail pressure indicates a sticking fuel pressure regulator.

Scan Tool Set-up for Fuel Pressure Regulator Diagnosis

  1. Using the scan tool, navigate to Fuel System Data. Select the Diagnostic Data Display tab and lock the following parameters: Engine Speed, Desired Fuel Rail Pressure, and Fuel Rail Pressure Sensor. Then select the Line Graph tab.
  2. Set up the following ranges for graphing the fuel rail pressure on the scan tool. The graph settings can be found by clicking on the arrow located in the middle on the right side of the page.
    • Engine Speed range 0 - 8, 000 RPM. This is the default setting.
    • Fuel Rail Pressure Sensor range -80 - 100 MPa (-11, 603 - 14, 504 PSI). Click on the Expand Y Axis button until the correct range is achieved.
    • Desired Fuel Rail Pressure range -80 - 100 MPa (-11, 603 - 14, 504 PSI). Click on the Expand Y Axis button until the correct range is achieved.

Fuel Pressure Regulator 1

  1. Engine idling.
  2. Engine at operating temperature
  3. Engine idle stable for 1 minute.
  4. Using scan tool control function Fuel Pressure Control - Regulator 1, increase and decrease fuel pressure.
  5. Observe the live plot for sharp changes or shark tooth pattern in the Fuel Rail Pressure while performing the following actions:
    • Slowly increase engine speed to 1800 RPM and then back to idle.
    • While at idle, shift the automatic transmission, if equipped, from Park to Drive and back to Park
    • Turn the air conditioning ON and OFF
  6. Verify a violent fluctuation in the Fuel Rail Pressure is not displayed, as seen in the surging graph below.
    • Go to next step: If a violent fluctuation in the Fuel Rail Pressure is not displayed 

Fuel Pressure Regulator 2

  1. Engine idling.
  2. Engine at operating temperature
  3. Engine idle stable for 1 minute.
  4. Using scan tool control function Fuel Pressure Control - Regulator 2, increase and decrease fuel pressure.
  5. Observe the live plot for sharp changes or shark tooth pattern in the Fuel Rail Pressure while performing the following actions:
    • Slowly increase engine speed to 1800 RPM and then back to idle.
    • While at idle, shift the automatic transmission, if equipped, from Park to Drive and back to Park
    • Turn the air conditioning ON and OFF
  6. Verify a violent fluctuation in the Fuel Rail Pressure is not displayed, as seen in the surging graph below.
    • Go to next step: If a violent fluctuation in the Fuel Rail Pressure is not displayed 
  7. All OK.
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